This invention pertains to an electro- or magneto-optic device wherein an electric or magnetic field is imposed to modify the optical properties of a fluid suspension in the device, to the method by which the optical properties are modified, and to applications therefor, such as electrically controlled shutters and electronic information displays.
Electrooptic effects using dipole suspensions of needle-like particles have been known since the late 1960s (A. M. Marks, Applied Optics, Volume 8, page 1397 (1969)). More recently, application of these effects by placement of the dipole suspension in a porous material has been suggested (G. Beni, H. G. Craighead, and S. Hackwood, Applied Physics Letters, Volume 39, page 195 (1981)).
With respect to dipole platelets, as contrasted with needles, a variety of crystalline, platelet materials have been known; however, the dipole characteristic of such platelets may not have been recognized. Typically such platelets are made up of thin transparent crystal layers of high refractive index which impart a particular light reflective characteristic to the platelets. This characteristic is observable as a pearlescent or iridescent effect. Such platelets are commonly used in decorative and cosmetic applications and are referred to as nacreous pigments. See for example "Nacreous Pigments", L. M. Greenstein and Encyclopedia of Polymer Science and Technology, Volume 10, published by John Wiley and Son (1969).
The chemical composition of common pigments of this type include various organic compounds, such as guanine; and inorganic materials, e.g. basic lead carbonate, bismuth oxychloride, lead hydrogen arsenate and lead hydrogen phosphate, and titanium dioxide coated mica. Pearlescent properties have also been reported for nafoxidine hydrochloride, an organic material which has been otherwise described in the technical literature with reference to its liquid crystalline properties in concentrated water solution and for its physiologic effect as an estrogen antagonist.
Notwithstanding this background knowledge, there have been relatively few practical applications of electrooptic effects in dipole needle suspensions and, to applicant's knowledge, a total absence of any suggestion to use nacreous pigment-type material in any sort of electro- or magneto-optic device. Moreover, currently available electrooptic devices and methods tend to be unsuitable for use in large area applications. Accordingly there appears to be a potentially significant need for more practical addressable, optical devices and methods.
It is the general object of the present invention, therefore, to provide an electro- or magneto-optic device (and method) which is potentially more practical for large applications than those heretofore available.